1. Field of the Invention
The present invention relates to an adhesion promoter additive comprising an unsaturated, amorphous polyester.
2. Discussion of the Background
Unsaturated polyester resins (UP resins) are well known. They are prepared by condensing saturated and unsaturated dicarboxylic acids or their anhydrides with diols. Their properties depend substantially on the nature and proportion of the starting materials.
The carrier of the polymerizable double bonds used are usually xcex1,xcex2-unsaturated acids, primarily maleic acid and its anhydride or fumaric acid; unsaturated diols are of minor importance. The higher the amount of double bonds, i.e., the smaller the separation of the double bonds in the chain molecules, the more reactive the polyester resin. It polymerizes very rapidly with intense development of heat and extensive contraction to give a highly crosslinked and therefore comparatively brittle end product. For this reason, the reactive double bonds in the polyester molecule are xe2x80x9cdilutedxe2x80x9d by co-condensing saturated aliphatic or aromatic dicarboxylic acids. The alcohol components used are straight-chain and/or branched diols. The individual UP resin types differ not only in the components used to prepare them but also in the ratio of saturated to unsaturated acids, which determines the crosslinking density in the polymerization, the degree of condensation, i.e., the molar mass, the acid number and the OH number, i.e., the type of end groups in the chain molecules, the monomer content, and the type of additives (Ullmann""s Encyclopedia of Industrial Chemistry, Vol. A21, p. 217ff, 1992).
UP resins based on dicidol as the diol component are known, for example, from DE 924 889, DE 953 117, DE 22 45 110, DE 27 21 989, EP 114 208 and EP 934 988.
The use of unsaturated polyester resins to promote adhesion is known, for example, from DE 24 09 800, EP 114 208, and EP 934 988.
It is an object of the present invention to provide an adhesion promoter additive which enhances properties of coating materials, such as the adhesion of coating materials, and at the same time exhibits high corrosion protection, high hardness, improved gloss and solids content, and lower contraction in the case of crosslinked systems. This and other objects have been achieved by the present invention the first embodiment of which includes an adhesion promoter additive, comprising:
at least one unsaturated, amorphous polyester comprising
1) an acid component comprising at least one xcex1,xcex2-unsaturated dicarboxylic acid, and
2) an alcohol component;
wherein said alcohol component comprises at least 5% of a dicidol mixture of the isomeric compounds
a) 3,8-bis(hydroxymethyl)tricyclo[5.2.1.02,6]decane,
b) 4,8-bis(hydroxy-methyl)tricyclo[5.2.1.02,6]decane, and
c) 5,8-bis-(hydroxymethyl)tricyclo[5.2.1.02,6]decane;
wherein each isomer is present in said dicidol mixture in a proportion of from 20 to 40% by weight; and
wherein a sum of said isomeric compounds a)-c) is from 90 to 100% by weight based on said dicidol mixture.